1. Field of the Invention
This invention relates to a magnetic tape wind-up method for winding a magnetic tape around a wind-up core in a roll shape, and an apparatus for carrying out the method. This invention particularly relates to a magnetic tape wind-up method wherein a magnetic tape is quickly wound up around a wind-up core into a large diameter roll in an aligned winding appearance, and an apparatus for carrying out the method.
2. Description of the Prior Art
In processes for making a magnetic tape such as a video tape, the magnetic tape is cut by a slitter to a predetermined width, and wound up around a wind-up core having no flange, which is generally called the pancake. The magnetic tape wound up around the wind-up core is then rewound around a plurality of tape reels and used in cassettes or the like.
When the magnetic tape is wound up around the wind-up core as described above, it is desired to wind as long a tape as possible around the wind-up core, i.e. into a roll having as large a diameter as possible. Also, in order to efficiently winding up the magnetic tape around the wind-up core, the wind-up speed should be as high as possible. The possibility of increasing the diameter of the magnetic tape roll wound up around the wind-up core and the wind-up speed depends on the decorative winding accuracy for aligning the appearance of the tape roll wound up around the wind-up core. Specifically, when the decorative winding accuracy is low, disturbance of winding appearance of the magnetic tape arises if the speed of winding up the magnetic tape is increases. Also, if the magnetic tape is wound up into a large diameter roll, disturbance of the winding appearance arises at a larger diameter section of the roll, and the roll of the magnetic tape wound around the wind-up core readily deforms. In order to achieve decorative winding of the magnetic tape at a high accuracy around the wind-up core, it is necessary to feed the magnetic tape accurately in a predetermined direction with respect to the wind-up surface of the wind-up core and to control the position of the magnetic tape in the width direction so that the side edges of respective turns of the wound-up magnetic tape align. Further, when air is confined between the respective turns of the wound-up magnetic tape, the respective turns of the wound-up magnetic tape readily slide against each other, and the roll of the magnetic tape wound-up readily deforms Therefore, it is necessary to sufficiently discharge confined air.
FIG. 3 is a schematic plan view showing the conventional magnetic tape wind-up apparatus. In the conventional magnetic tape wind-up apparatus, a magnetic tape 1 is wound up around a wind-up core 3 rotated in the direction as indicated by the arrow A. The magnetic tape 1 is fed via a guide roller 2, and the position of the magnetic tape 1 is controlled only by a touch roller 13 which is urged by a spring or the like (not shown) to resiliently push the magnetic tape 1 against a tape roll 1' previously formed around the wind-up core 3 at the position where the magnetic tape 1 reaches the tape roll 1'. That is, the touch roller 13 must simultaneously effect both the control of the position of the magnetic tape 1, the position of which has been restricted to some extent by the guide roller 2, in the width direction thereof and air discharging from spaces between respective turns of the tape roll 1'. Therefore, in the conventional apparatus merely provided with the touch roller 13, it is not always possible to substantially improve the decorative winding accuracy of the magnetic tape and to increase the diameter of the magnetic tape roll and the wind-up speed. Particularly, as the magneiic tape has been improved in recent years, magnetic tapes which are very thin and have smooth surfaces are now widely used. The thin magnetic tapes readily bend or deform during tape winding. Also, the magnetic tapes having smooth surfaces slide more readily than conventional magnetic tapes, and the tape roll deforms readily when even a very small amount of air is present between the respective turns of the tape roll. Therefore, with the conventional wind-up technique, it is not always possible to satisfactorily wind up the magnetic tapes which are thin and/or have smooth surfaces.